Heat source system and control method therefor

ABSTRACT

The purpose of the present invention is to maintain a water supply temperature close to a target water supply temperature at the time of a change in the number of heat source machines operating. A heat source system of the present invention anticipates a case where a prescribed minimum flow rate is set for heat source machines that are subject to addition or removal, and calculates, as compensation temperatures, hot and cold water outlet temperatures of the heat source machines so that the water supply temperature in such a case will match a target water supply temperature, and changes the hot and cold water outlet temperature settings of the operating heat source machines to the compensation temperatures. After that, the heat source machines that are subject to addition or removal are either started up or stopped, and the set flow rate for the heat source machines that are subject to addition or removal is set to the minimum flow rate.

This application is a Divisional of copending application Ser. No.14/429,271, filed on Mar. 18, 2015, which is the National Phase under 35U.S.C, § 371 of International Application No. PCT/JP2013/075358, filedon Sep. 19, 2013, which claims the benefit under 35 U.S.C. § 119(a) toPatent Application Nos. 2012-208957 and 2013-038957, filed in Japan onSep. 21, 2012 and Feb. 28, 2013, all of which are hereby expresslyincorporated by reference into the present application.

TECHNICAL FIELD

The present invention relates to a heat source system and a controlmethod thereof.

BACKGROUND ART

In the related art, a heat source system is known in which plural heatsource machines are connected in parallel (for example, see PTL 1), Insuch a heat source system, the heat source machines are generallyoperated such that the temperature of cold/hot water (hereinafter,referred to as “supply water temperature”) sent out from the heat sourcemachine side to a load side becomes equal to a target supply watertemperature (for example, 7° C.) set by a load-side request.

In operation, when the number of heat source machines operatingincreases and a stopped heat source machine is started, time is requireduntil the capability of the heat source machine is exercised.Accordingly, the supply water temperature temporarily has a valueseparated from the target supply water temperature and cold/hot watercannot be stably supplied to the load side.

In the related art, the following solution has been proposed for such aproblem.

For example, PTL 1 discloses a method of suppressing a rise in supplywater temperature by setting the set value of a cold/hot water outlettemperature of a refrigerator to be lower than a currently-set value anda method of causing the supply water temperature to approach a targettemperature by setting the flow rate of a refrigerator in operation tobe greater than an anticipated flow rate at the time of adding orsubtracting a refrigerator.

PTL 2 discloses that a supply water temperature is prevented from beingseparated from a target temperature by changing the set value of anoutlet temperature of a heat source machine when the number of pumpsoperating is different from the number of refrigerators operating.

CITATION LIST Patent Literature

[PTL 1] Japanese Unexamined Patent Application Publication No.2005-114295

[PTL 2] Japanese Unexamined Patent Application Publication No.2004-278884

SUMMARY OF INVENTION Technical Problem

However, in the method disclosed in PTL 1, when the set value of thecold/hot water outlet temperature of the heat source machine isexcessively lowered, the supply water temperature is also excessivelylowered and there is a possibility that the supply water temperaturewill be separated from a target supply water temperature. On thecontrary, when the set value is insufficiently lowered, the rise in thesupply water temperature can be suppressed in comparison with a case inwhich the set value is not changed, but there is a possibility that thesupply water temperature will be much higher than the target supplywater temperature requested by the load side in this case.

As disclosed in PTL 1, when the flow rate of a refrigerator in operationis set to be higher than an anticipated flow rate, it is possible tosuppress the rise in the supply water temperature. However, when thecold water outlet setting temperature of the refrigerator is notlowered, the supply water temperature generally becomes higher than thetarget supply water temperature. In order to avoid this problem, whenthe cold water outlet setting temperature of the refrigerator is loweredas described above, there is a possibility that the supply watertemperature will be excessively lowered depending on the degree oflowering.

In the method disclosed in PTL 2, there is a possibility that the supplywater temperature will be separated from the target temperature untilthe outlet temperature of the refrigerator reaches the changed settingtemperature.

The present invention is made in consideration of the aforementionedcircumstances and an object thereof is to provide a heat source systemthat can keep a supply water temperature in the vicinity of a targetsupply water temperature when changing the number of heat sourcemachines operating and a control method thereof.

Solution to Problem

According to a first aspect of the present invention, there is provideda heat source system that includes a plurality of heat source machinesconnected in parallel to a load and that controls operations of the heatsource machines such that a supply water temperature of cold/hot waterwhich is supplied to the load corresponds to a target supply watertemperature which is determined by a load-side request, the heat sourcesystem including: temperature calculating means for anticipating a casein which a predetermined flow rate is set for the heat source machine tobe added or subtracted when changing the number of heat source machinesoperating and calculating a cold/hot water outlet temperature of theheat source machine in operation as a compensation temperature such thatthe supply water temperature at that time corresponds to the targetsupply water temperature; and temperature setting means for changing acold/hot water outlet setting temperature of the heat source machine inoperation to the compensation temperature, wherein the heat sourcemachine to be added or subtracted is started or stopped and the settingflow rate of the heat source machine to be added or subtracted is set tothe predetermined flow rate, after the supply water temperature ischanged with the changing of the cold/hot water outlet settingtemperature of the heat source machine in operation.

According to this aspect, when changing the number of heat sourcemachines operating, the change in the supply water temperature when aheat source machine is added or subtracted is predicted in advance, thecold/hot water outlet temperature of the heat source machine of whichthe supply water temperature reaches the target supply water temperatureis calculated as the compensation temperature, and the compensationtemperature is set as the cold/hot water outlet setting temperature ofthe heat source machine in operation. Accordingly, for example, when aheat source machine is added, the capability shortfall in a period untilthe capability is exercised after the heat source machine to beadditionally started is started can be supplemented with the heat sourcemachines in operation. When a heat source machine is subtracted, thecapability shortfall can be supplemented with the heat source machinesoperating even in a state in which the heat source machine to be stoppeddoes not exercise its capability. As a result, it is possible to preventthe supply water temperature from being separated from the target supplywater temperature when a heat source machine is actually added orsubtracted and it is possible to supply cold/hot water, of which thetemperature is stabilized, to an external load even when changing thenumber of heat source machines operating.

The expression, “after the supply water temperature is changed with thechange in the cold/hot water outlet setting temperature of the heatsource machines in operation”, means after a predetermined amount oftime elapses after the cold/hot water outlet setting temperature of theheat source machines is changed to the compensation temperature or afterthe supply water temperature or the cold/hot water outlet temperaturesof the heat source machines enter the allowable temperature range set tobe close to the compensation temperature. The “predetermined amount oftime” is empirically set on the basis of the amount of time requireduntil the supply water temperature or the cold/hot water outlettemperatures of the heat source machines enter the allowable temperaturerange set to be close to the compensation temperature.

In the heat source system, the temperature calculating means maycalculate the compensation temperature, for example, using anoperational expression including the cold/hot water outlet temperatureof the heat source machine to be added or subtracted, the flow rate ofcold/hot water flowing in the heat source machine to be added orsubtracted, and the flow rate of cold/hot water in the heat sourcemachine which has already operated and which continuously operates afterthe addition or subtraction as parameters.

In the heat source system, the cold/hot water outlet temperatures of allthe heat source machines in operation may be set to the target supplywater temperature at the time of adding the heat source machine when theheat source machine to be added is started and it is determined that thecold/hot water outlet temperature of the heat source machine to be addedis in an allowable temperature range set to be close to the targetsupply water temperature.

The expression, “when it is determined that the cold/hot water outlettemperature of the heat source is in the allowable temperature range setto be close to the target supply water temperature”, means that, forexample, when a predetermined amount of time elapses after the heatsource machine is started as well as when the cold/hot water outlettemperature of the heat source machine enters the allowable temperaturerange, the cold/hot water outlet temperature of the heat source machineis considered to be in the allowable temperature range. In this case,the cold/hot water outlet setting temperature may be changed.

In the heat source system, the cold/hot water outlet settingtemperatures of all the heat source machines in operation may be set tothe target supply water temperature in subtracting the heat sourcemachine when the heat source machine to be subtracted is started and apredetermined amount of time elapses after the heat source is subtractedor water supply means provided to correspond to the heat source machineto be subtracted is stopped.

In the heat source system, the temperature calculating means may set thecompensation temperature to a predetermined temperature upper limit setin advance on the basis of capability of the heat source machine whenthe compensation temperature is higher than the temperature upper limit.

In the heat source system, the temperature calculating means may set thecompensation temperature to a predetermined temperature lower limit setin advance on the basis of capability of the heat source machine whenthe compensation temperature is lower than the temperature lower limit.

By employing this configuration, it is possible to avoid separation ofthe supply water temperature from the target supply water temperatureand to prevent a trip of the heat source machine in operation.

In the heat source system, the temperature calculating means maycalculate the compensation temperature using the flow rate of the heatsource in operation as a maximum flow rate, and the cold/hot wateroutlet setting temperature of the heat source in operation may bechanged to the compensation temperature and the setting flow ratethereof is changed to the maximum flow rate.

According to this heat source system, it is possible to broaden thecontrol width of the supply water temperature by additionally performingthe flow rate control in addition to the temperature control, and it ispossible to cause the heat source machine in operation to furtherexercise its capability. Accordingly, it is possible to supplement thecapability shortfall when the heat source machine to be added orsubtracted is additionally started or stopped with the heat sourcemachines in operation as much as possible and it is possible to furthersuppress the variation in the supply water temperature when changing thenumber of heat source machines operating.

In the heat source system, the temperature recalculating means maycalculate the compensation temperature using the flow rate of the heatsource machine in operation as a maximum flow rate when the compensationtemperature departs from a predetermined temperature upper-lower limitrange set in advance on the basis of capability of the heat sourcemachine, and the cold/hot water outlet setting temperature of the heatsource machine in operation may be set to the recalculated compensationtemperature and the setting flow rate is set to the maximum flow rate.

By employing this configuration, the flow rate can be adjusted only in asituation which cannot be coped with by only changing the temperature,and it is thus possible to skip unnecessary flow rate adjustment.

In the heat source system, it may be determined whether an operationstate of the heat source machine in operation reaches a capability upperlimit after the cold/hot water outlet setting temperature of the heatsource machine in operation is set to the compensation temperature bythe temperature setting means at the time of adding the heat sourcemachine, and the heat source machine to be added may be immediatelystarted when the operation state of the heat source machine reaches thecapability upper limit.

According to this heat source system, when the capability of the heatsource machine continuously operating reaches the upper limit, it ispossible to skip an unnecessary determination process and to rapidlystart the heat source machine to be added.

The heat source system may further include temperature measuring meansfor measuring a return water temperature from the load, and thetemperature calculating means may calculate the compensation temperatureusing the return water temperature measured by the temperature measuringmeans as the cold/hot water outlet temperature of the heat sourcemachine to be added or subtracted.

Accordingly, it is possible to easily calculate the compensationtemperature.

In the heat source system, the temperature calculating means maycalculate a theoretical value of the return water temperature on thebasis of a relationship among a heat source load, a heat quantity ofcold/hot water sent out from the system to the external load, and a heatquantity of cold/hot water flowing into the system, and may calculatethe compensation temperature using theoretical value of the return watertemperature as the cold/hot water outlet temperature of the heat sourcemachine to be added or subtracted.

In this way, it is possible to improve the estimation accuracy of thecold/hot water outlet temperature of the heat source machine to be addedor subtracted by using theoretical value of the return water temperatureas the cold/hot water outlet temperature of the heat source machine tobe added or subtracted at the time of calculating the compensationtemperature. Accordingly, it is possible to improve the calculationaccuracy of the compensation temperature and to bring the supply watertemperature closer to the target supply water temperature when changingthe number of heat source machines.

The heat source system may further include temperature measuring meansfor measuring a return water temperature from the load, and thetemperature calculating means may calculate a theoretical value of thereturn water temperature on the basis of a relationship among a heatsource load, a heat quantity of cold/hot water sent out from the systemto the external load, and a heat quantity of cold/hot water flowing intothe system and may calculate the compensation temperature using thereturn water temperature, which is calculated using both the measuredvalue of the return water temperature measured by the temperaturemeasuring means and the theoretical value of the return watertemperature as parameters, as the cold/hot water outlet temperature ofthe heat source machine to be added or subtracted.

For example, when only the measured value of the return watertemperature is used, the compensation temperature at the current time iscalculated. On the other hand, when theoretical value is used, thecompensation temperature in a future situation is calculated. Forexample, when a heat source machine is added or subtracted, the measuredvalue is changed to correspond to theoretical value, the change in thecompensation temperature becomes slower when the measured value isslowly changed, and the heat source machines can track the change in thecompensation temperature. However, when the compensation temperature iscalculated using the measured value of the return water temperature asthe cold/hot water outlet temperature of the heat source machine to beadded or subtracted and the return water temperature is rapidly changed,the compensation temperature is accordingly rapidly changed. Then, thereis a possibility that the heat source machines will not track the changein the compensation temperature and the supply water temperature will beseparated from the target supply water temperature. Accordingly, bycalculating the return water temperature using both theoretical valueand the measured value as parameters in consideration of such asituation and considering the return water temperature as the cold/hotwater outlet temperature of the heat source machine to be added, it ispossible to prevent the supply water temperature from being separatedfrom the target supply water temperature.

In the heat source system, the temperature calculating means maycalculate the compensation temperature using a correction value obtainedby multiplying a predetermined coefficient equal to or greater than zeroand equal to or less than 1 by a value, which is obtained by subtractingtheoretical value of the return water temperature from the measuredvalue of the return water temperature measured by the temperaturemeasuring means.

In this way, by calculating the compensation temperature using thecorrection value based on the difference between theoretical value andthe measured value of the return water temperature, it is possible tobring the supply water temperature close to the target supply watertemperature even when the return water temperature departs fromtheoretical value thereof.

In the heat source system, a change rate may be set to be lower than apredetermined change rate set on the basis of tracking capability of theheat source machine in operation when increasing the cold/hot water flowrate of the heat source machine to be added.

According to this heat source system, even when the cold/hot water flowrate of the heat source machine to be added increases, the change in thesupply water temperature due to the increase in the flow rate isabsorbed by capability of the heat source machines in operation and itis thus possible to keep the supply water temperature close to thetarget supply water temperature.

In the heat source system, the cold/hot water outlet setting temperatureof the heat source machine to be subtracted may be changed to apredetermined temperature set in advance at a predetermined change rateto lower the load of the heat source machine to be subtracted whensubtracting the heat source machine, an operation stop instruction maybe given to the heat source machine to be subtracted, and the cold/hotwater outlet setting temperature of the heat source in operation may bechanged to the target supply water temperature.

According to this heat source system, by changing the cold/hot wateroutlet temperature of the heat source machine to be subtracted to apredetermined temperature set in advance at a predetermined change rate,the load of the heat source machine to be subtracted is intentionallyslowly lowered, then the corresponding heat source machine is stopped,and the cold/hot water outlet temperature of the heat source machines inoperation is changed to the target supply water temperature.Accordingly, it is possible to absorb the change in the supply watertemperature at the time of subtracting a heat source machine by causingthe heat source machines in operation to exercise their capability andto keep the supply water temperature close to the target supply watertemperature.

In the heat source system, the change rate may be set to a change ratein a range in which an overshoot or an undershoot of the cold/hot wateroutlet temperature with respect to the cold/hot water outlet settingtemperature of the heat source machine in operation does not occur whenchanging the cold/hot water outlet setting temperature of the heatsource machine in operation from the compensation temperature to thetarget supply water temperature.

Accordingly, it is possible to suppress separation of the supply watertemperature from the target supply water temperature, which occurs whenchanging the cold/hot water outlet setting temperature of the heatsource machine in operation from the compensation temperature to thetarget supply water temperature.

In the heat source system, the compensation temperature may berecalculated so as to distribute a heat quantity shortfall of the heatsource machines to the other heat source machines in operation of whichthe capability does not reach the capability upper limit and thecold/hot water outlet setting temperature of the other heat sourcemachines in operation of which the capability does not reach thecapability upper limit may be set to the recalculated compensationtemperature when the operation states of some heat source machines inoperation reach the capability upper limit and the cold/hot water outlettemperature of the heat source machines in operation does not reach thecompensation temperature after the cold/hot water outlet settingtemperature of at least the heat source machines in operation is set tothe compensation temperature by the temperature setting means.

By employing this configuration, when the cold/hot water outlet settingtemperature of a heat source machine in operation is changed to thecompensation temperature and there is a heat source machine that cannottrack the compensation temperature due to the capability shortfallthereof, it is possible to supplement the capability shortfall with theother heat source machines in operation which does not reach thecapability upper limit. Accordingly, it is possible to effectively usethe capability of the heat source machines in operation.

In the heat source system, the temperature calculating means maycalculate the compensation temperature using the cold/hot water outlettemperature of the heat source machines, or the lower temperature of thecold/hot water outlet temperature and the return water temperature whencooling a heat medium, or the higher temperature of the cold/hot wateroutlet temperature and the return water temperature when heating theheat medium as the cold/hot water outlet temperature of the heat sourcemachine to be added after the heat source machine to be added isstarted.

Accordingly, after the heat source machine to be added is started, it ispossible to calculate the compensation temperature of the heat sourcemachines in operation in consideration of the temperature change of thecold/hot water outlet temperature of the heat source machine to beadded. As a result, it is possible to control the supply watertemperature so as to be close to the target supply water temperaturewhile the heat source machine to be added gradually exercises itscapability.

The heat source system may further include temperature measuring meansfor measuring a cold/hot water outlet temperature or a cold/hot waterinlet temperature of the heat source machine, and the temperaturecalculating means may calculate the compensation temperature using themeasured value, which has been measured by the temperature measuringmeans provided to correspond to the heat source machine to be added orsubtracted, as the cold/hot water outlet temperature of the heat sourcemachine to be added or subtracted.

In this way, since the cold/hot water outlet temperature or the cold/hotwater inlet temperature of the heat source machine to be added orsubtracted is measured by the temperature measuring means and thecompensation temperature is calculated using the measured value, it ispossible to improve the accuracy of the compensation temperature.

In the heat source system, the predetermined flow rate of the heatsource machine to be added may be set within a range equal to or higherthan a minimum flow rate of a cold/hot water pump provided to correspondto the heat source machine to be added and equal to or lower than aminimum flow rate determined on the basis of a specification of the heatsource machine to be added.

Accordingly, it is possible to supply the cold/hot water of the heatsource machine to be added at a low flow rate and thus to reduce theinfluence which the temperature of the cold/hot water in the heat sourcemachine to be added gives to the supply water temperature. Accordingly,for example, even when the temperature of the cold/hot water in the heatsource machine to be added is separated from the return watertemperature, it is possible to prevent the supply water temperature frombeing greatly separated from the target supply water temperature.

In the heat source system, the predetermined flow rate of the heatsource machine to be subtracted may be set to a minimum flow ratedetermined on the basis of a specification of the heat source machine tobe subtracted.

In this way, by setting the predetermined flow rate to the minimum flowrate determined on the basis of the specification of the heat sourcemachine to be subtracted, it is possible to reduce the influence whichthe cold/hot water sent out from the heat source machine to besubtracted gives to the supply water temperature.

In the heat source system, the temperature calculating means may have aweighting set on the basis of an influence which the cold/hot water sentout from each heat source machine gives to the supply water temperaturefor each heat source machine and may calculate the compensationtemperature using the weighting.

In this way, since each heat source machine has a weighting set on thebasis of the influence which the cold/hot water sent out from the heatsource machine gives to the supply water temperature and thecompensation temperature is calculated using the weighting, it ispossible to improve the calculation accuracy of the compensationtemperature.

According to a second aspect of the present invention, there is provideda control method of a heat source system that includes a plurality ofheat source machines connected in parallel to a load and that controlsoperations of the heat source machines such that a supply watertemperature of cold/hot water which is supplied to the load correspondsto a target supply water temperature which is determined by a load-siderequest, the control method including: a step of anticipating a case inwhich a predetermined flow rate is set for the heat source machine to beadded or subtracted when changing the number of heat source machinesoperating and calculating a cold/hot water outlet temperature of theheat source machine in operation as a compensation temperature such thatthe supply water temperature at that time corresponds to the targetsupply water temperature; and a step of changing a cold/hot water outletsetting temperature of the heat source machine in operation to thecompensation temperature, wherein the heat source machine to be added orsubtracted is started or stopped and the setting flow rate of the heatsource machine to be added or subtracted is set to the predeterminedsetting flow rate, after the supply water temperature is changed withthe changing of the cold/hot water outlet setting temperature of theheat source machine in operation.

Advantageous Effects of Invention

According to the present invention, it is possible to keep the supplywater temperature in the vicinity of the target supply watertemperature.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram schematically illustrating a configuration of a heatsource system according to a first embodiment of the present invention.

FIG. 2 is a flowchart illustrating a supply water temperaturecompensating process according to the first embodiment of the presentinvention.

FIG. 3 is a flowchart illustrating the supply water temperaturecompensating process according to the first embodiment of the presentinvention.

FIG. 4 is a diagram illustrating the supply water temperaturecompensating process illustrated in FIGS. 2 and 3.

FIG. 5 is a flowchart illustrating a supply water temperaturecompensating process according to a third embodiment of the presentinvention.

FIG. 6 is a flowchart illustrating the supply water temperaturecompensating process according to the third embodiment of the presentinvention.

FIG. 7 is a flowchart illustrating the supply water temperaturecompensating process according to the third embodiment of the presentinvention.

FIG. 8 is a flowchart illustrating an example of a supply watertemperature compensating process according to a fourth embodiment of thepresent invention.

FIG. 9 is a flowchart illustrating an example of a supply watertemperature compensating process according to a seventh embodiment ofthe present invention.

FIG. 10 is a flowchart illustrating an example of the supply watertemperature compensating process according to the seventh embodiment ofthe present invention.

FIG. 11 is a flowchart illustrating an example of the supply watertemperature compensating process according to the seventh embodiment ofthe present invention.

FIG. 12 is a diagram illustrating an example of an overshoot whichoccurs when a cold/hot water outlet setting temperature is step-likechanged in a heat source system according to an eighth embodiment of thepresent invention.

FIG. 13 is a diagram illustrating an effect in the heat source systemaccording to the eighth embodiment of the present invention.

FIG. 14 is a flowchart illustrating an example of a supply watertemperature compensating process according to a ninth embodiment of thepresent invention.

FIG. 15 is a flowchart illustrating an example of the supply watertemperature compensating process according to the ninth embodiment ofthe present invention.

FIG. 16 is a flowchart illustrating an example of the supply watertemperature compensating process according to the ninth embodiment ofthe present invention.

FIG. 17 is a flowchart illustrating an example of the supply watertemperature compensating process according to the ninth embodiment ofthe present invention.

FIG. 18 is a flowchart illustrating an example of a supply watertemperature compensating process according to a twelfth embodiment ofthe present invention.

FIG. 19 is a flowchart illustrating an example of the supply watertemperature compensating process according to the twelfth embodiment ofthe present invention.

DESCRIPTION OF EMBODIMENTS First Embodiment

Hereinafter, a heat source system and a control method thereof accordingto a first embodiment of the present invention will be described withreference to the accompanying drawings.

FIG. 1 is a diagram schematically illustrating a configuration of a heatsource system according to the first embodiment of the presentinvention. A heat source system 1 includes plural heat source machines10 a, 10 b, and 10 c that cool a heat medium (cold water) to be suppliedto an external load 2 such as an air conditioner, a water heater, and aplant facility. The heat source machines 10 a, 10 b, and 10 c areconnected in parallel to the external load 2. In FIG. 1, three heatsource machines 10 a, 10 b, and 10 c are provided, but the number ofheat source machines installed can be arbitrarily determined.

Cold/hot water pumps 3 a, 3 b, and 3 c pumping heat mediums are disposedon the upstream side of the heat source machines 10 a, 10 b, and 10 c inthe heat medium flow. Heat mediums from the return head 4 are suppliedto the heat source machines 10 a, 10 b, and 10 c by the cold/hot waterpumps 3 a, 3 b, and 3 c. The cold/hot water pumps 3 a, 3 b, and 3 c aredriven by an inverter motor (not illustrated) and thus the flow ratesthereof are controlled to be variable by varying the rotation speed.

The heat mediums cooled or heated by the heat source machines 10 a, 10b, and 10 c gather in a supply header 5. The heat mediums gathering inthe supply header 5 is supplied to the external load 2. The heat mediumswhich have been provided to air-conditioning in the external load 2 andof which the temperature has risen or fallen are sent to the returnheader 4. The heat mediums are branched in the return header 4 and aresent again to the heat source machines 10 a, 10 b, and 10 c.

A bypass pipe 6 is disposed between the supply header 5 and the returnheader 4. The bypass pipe 6 is provided with a bypass valve 7 foradjusting a bypass flow rate.

The heat source machines 10 a, 10 b, and 10 c are connected to anupper-level controller 20 via a communication medium and both caninteractively communicate.

The upper-level controller 20 is, for example, a controller thatcontrols the heat source system as a whole and performs supply watertemperature control of setting a cold/hot water outlet set temperaturesof the heat source machines 10 a, 10 b, and 10 c such that the supplywater temperature of cold/hot water supplied to the external load 2 isequal to a target supply water temperature determined by a request ofthe external load 2, controlling of the number of heat source machines10 a, 10 b, and 10 c operating based on a request load of the externalload 2, rotation speed control of the pumps 3 a, 3 b, and 3 c, valveopening control of the bypass valve 7 based on the pressure differencebetween the supply header 5 and the return header 4, and the like.

The upper-level controller 20 is, for example, a computer and includes acentral processing unit (CPU), a main storage device such as a randomaccess memory (RAM), an auxiliary storage device, and a communicationdevice that transmits and receives information by communication with anexternal device.

The auxiliary storage device is a computer-readable recording medium andexamples thereof include a magnetic disk, a magneto-optical disk, aCD-ROM, a DVD-ROM, and a semiconductor memory. Various programs arestored in the auxiliary storage device and various processes arerealized by causing the CPU to read the programs from the auxiliarystorage device into the main storage device and to execute the readprograms.

FIG. 2 is a flowchart illustrating a supply water temperaturecompensating process which is performed at the time of changing thenumber of heat source machines operating in the supply water temperaturecontrol out of various control functions of the upper-level controller20.

For example, as illustrated in FIG. 4, when the heat source machines 10a and 10 b operate already (hereinafter, a heat source machine operatingalready is referred to as an “operating heat source”) and the targetsupply water temperature is set to 7° C., the cold/hot water outletsetting temperature of the heat source machines 10 a and 10 b is set to7° C. which is equal to the target supply water temperature 7° C. Inthis state, when the heat source machine 10 c is newly added, cold/hotwater (for example, 12° C.) close to the return water temperature (thetemperature of cold/hot water supplied from the return header 4 to theheat source machines) is output from the heat source machine 10 c untilthe capability of the heat source machine 10 c is exercised after it isstarted. Accordingly, when the operations of the heat source machines 10a and 10 b are kept at the cold/hot water outlet setting temperature 7°C., the supply water temperature may be separated from 7° C. in adirection in which the temperature rises. This problem similarly occurswhen the number of heat source machines decreases.

The supply water temperature compensating process is to suppress theseparation of the supply water temperature from the target supply watertemperature at the time of changing the number of heat source machinesoperating and is to keep the supply water temperature of cold/hot waterclose to the target supply water temperature at the time of changing thenumber of heat source machines operating.

The supply water temperature compensating process will be describedbelow with reference to FIGS. 2 and 3.

First, when an addition or subtraction request is input (“YES” in stepSA1), a case in which a predetermined minimum flow rate determined onthe basis of the specification (capability) of the heat source machineis set for a heat source machine to be added or subtracted isanticipated, and the cold/hot water outlet temperature of the heatsource machine is calculated as the compensation temperature T_(set_u)such that the estimated supply water temperature at that time is equalto the target supply water temperature (temperature calculating means),Here, in this embodiment, the case in which a “predetermined minimumflow rate” is set for the heat source machine to be added or subtractedis anticipated, but the anticipated flow rate is not necessarily theminimum flow rate determined on the basis of the specification of theheat source machine.

Specifically, the compensation temperature T_(set_u) is calculated usingExpression (2) (step SA2).

For example, in the heat source system illustrated in FIG. 3, when acase in which the heat source machine 10 c is newly started and a heatmedium flows in the heat source machine 10 c at a minimum flow ratef_(n_min), Expression (1) needs to be established in order to make thesupply water temperature before the heat source machine 10 c exercisesits capability equal to the target supply water temperature.

$\begin{matrix}{{{T_{{set}\;\_\; u} \times {\sum\limits_{i = 1}^{n - 1}f_{i}}} + {t_{{ave}\;\_\; r} \times f_{n\;\_\; m\; i\;{nn}}}} = {T_{set} \times ( {{\sum\limits_{i = 1}^{n - 1}f_{i}} + f_{n\;\_\; m\; i\; n}} )}} & (1)\end{matrix}$

In Expression (1), T_(set) represents the target supply watertemperature, f_(i) represents the flow rate of cold/hot water flowing inan operating heat source machine, T_(set_u) represents a cold/hot wateroutlet setting temperature (=compensation temperature) of an operatingheat source machine, and t_(ave_r) represents the return watertemperature, which employs a time average of the measured temperaturevalues measured by a temperature sensor (temperature measuring means)disposed in the vicinity of the return header 4. The cold/hot wateroutlet setting temperature T_(set_u) of an operating heat source machinefor establishing Expression (1) is given by Expression (2).

$\begin{matrix}{T_{{set}\;\_\; u} = \frac{{T_{set}( {{\sum\limits_{i = 1}^{n - 1}f_{i}} + f_{n\;\_\; m\; i\; n}} )} - {f_{n\;\_\; m\; i\; n} \times t_{{ave}\;\_\; r}}}{\sum\limits_{i = 1}^{n - 1}f_{i}}} & (2)\end{matrix}$

The compensation temperature T_(set_u) is repeatedly calculated with apredetermined sampling cycle. Accordingly, the compensation temperatureT_(set_u) to be described later means the newest value at that time.This is true of the embodiments to be described later.

Then, it is determined whether a heat source machine is added (stepSA3). When it is determined that a heat source machine is added (“YES”in step SA3), the cold/hot water outlet setting temperatures of theoperating heat source machines are changed from the target supply watertemperature T_(set) to the compensation temperature T_(set_u) (stepSA4). Subsequently, it is determined whether a predetermined amount oftime elapses after the cold/hot water outlet setting temperature of theheat source machine is changed to the compensation temperature orwhether the supply water temperature or the cold/hot water outlettemperatures of the operating heat source machines are in an allowablerange set to be close to the compensation temperature T_(set_u) (stepSA5). When it is determined that the predetermined amount of timeelapses or that the supply water temperature or the cold/hot wateroutlet temperatures of the operating heat source machines are in theallowable range, a start instruction is output to the heat sourcemachine to be added and the flow rate of cold/hot water flowing into theheat source machine is se to the minimum flow rate, that is, the flowrate anticipated at the time of calculating the compensation temperatureT_(set_u) (steps SA6 and SA7).

Then, it is determined whether a predetermined amount of time elapsesafter a heat source machine is started or whether the cold/hot wateroutlet temperature of the started heat source machine (hereinafter,referred to as “added heat source machine”) is in an allowable range setto be close to the target supply water temperature T_(set) (step SA8).When it is determined that the predetermined amount of time elapses orthat the cold/hot water outlet temperatures are in the allowable range(“YES” in step SA8), the cold/hot water outlet setting temperature ofthe operating heat source machines are changed from the compensationtemperature T_(set_u) to the target supply water temperature T_(set)(step SA9) and then the supply water temperature compensating processends.

On the other hand, when it is determined in step SA3 that a heat sourcemachine is added, the cold/hot water outlet setting temperatures of theoperating heat source machines (which include the heat source machine tobe subtracted) is changed from the target supply water temperatureT_(set) to the compensation temperature T_(set_u), and the cold/hotwater setting flow rate of the heat source machine to be subtracted(hereinafter, referred to as “subtracted heat source machine”) ischanged to the minimum flow rate (steps SA10 and SA11 in FIG. 3). Instep SA10, instead of the operating heat source machines, the cold/hotwater outlet setting temperatures of the operating heat source machinesexcept the heat source machine to be subtracted may be changed from thetarget supply water temperature T_(set) to the compensation temperatureT_(set_u).

Subsequently, it is determined whether a predetermined amount of timeelapses after the cold/hot water outlet setting temperatures of theoperating heat source machines are changed to the compensationtemperature or whether the supply water temperature or the cold/hotwater outlet temperatures of the operating heat source machines are inan allowable range set to be close to the compensation temperatureT_(set_u) (step SA12). When the cold/hot water outlet settingtemperature of the heat source machine to be subtracted is not changedto T_(set_u) in step SA10, it is determined in step SA12 whether apredetermined amount of time elapses after the cold/hot water outletsetting temperatures of the operating heat source machines are changedto the compensation temperature or whether the cold/hot water outlettemperature of the operating heat source machines except the heat sourcemachine to be subtracted are in the allowable range set to be close toT_(set_u).

When it is determined that the predetermined amount of time elapses orthat the supply water temperature and the like are in the allowablerange, an operation stop instruction is output to the heat sourcemachine to be subtracted and the cold/hot water pump corresponding tothe heat source machine (step SA13).

Then, it is determined whether a predetermined amount of time elapsesafter the heat source machine subtracting instruction is given orwhether the cold/hot water pump corresponding to the heat source machineto be subtracted is stopped (step SA14). When it is determined that thepredetermined amount of time elapses or that the cold/hot water pump isstopped (“YES” in step SA14), the cold/hot water outlet settingtemperatures of the heat source machines in operation are changed fromthe compensation temperature T_(set_u) to the target supply watertemperature T_(set) (step SA15) and then the supply water temperaturecompensating process ends.

As described above, in the heat source system 1 according to thisembodiment and the control method thereof, when changing the number ofheat source machines operating, the change in the supply watertemperature when a heat source machine is added or subtracted isanticipated, the cold/hot water outlet temperature is calculated as thecompensation temperature T_(set_u) u such that the supply watertemperature is equal to the target supply water temperature T_(set), andthe compensation temperature T_(set_u) is set as the cold/hot wateroutlet setting temperatures of the operating heat source machines.

Accordingly, for example, when a heat source machine is added, it ispossible to supplement the capability shortfall with the operating heatsource machines in the period until the capability is exercised afterthe heat source machine to be additionally started is started. When aheat source machine is subtracted, it is possible to supplement theshortfall with the operating heat source machines in a state in whichthe heat source machine to be stopped does not exercise its capability.

As a result, it is possible to prevent the supply water temperature frombeing separated from the target supply water temperature when a heatsource machine is actually added or subtracted and it is thus possibleto supply cold/hot water with a stabilized temperature to the externalload even when changing the number of heat source machines operating.

In this embodiment, the compensation temperature T_(set_u) may be setfor a heat source machine to be added or subtracted in addition to theheat source machines which continuously operate.

Second Embodiment

A heat source system according to a second embodiment of the presentinvention and a control method thereof will be described below withreference to the accompanying drawings.

In the heat source system according to the first embodiment and thecontrol method thereof, the separation of the supply water temperaturefrom the target supply water temperature is avoided by supplementing thecapability shortfall of the heat source machine to be added orsubtracted with the operating heat source machines. However, forexample, there is a possibility that the compensation temperatureT_(set_u) departs from the operable range of the operating heat sourcesand causes a trip or the like.

Therefore, in order to avoid this problem, for example, an allowablerange of the cold/hot water outlet setting temperature based on thecapability of a heat source machine is set in advance and thecompensation temperature is made not to depart from the allowable range.

Specifically, when a heat medium is cooled, it is determined whether thecompensation temperature calculated in step SA2 in FIG. 2 is lower thanthe lower limit of the cold/hot water outlet setting temperatureregistered in advance. When the compensation temperature is lower thanthe lower limit, the lower limit of the cold/hot water outlet settingtemperature is set as the compensation temperature.

Similarly, when a heat medium is heated, it is determined whether thecompensation temperature calculated in step SA2 in FIG. 2 is higher thanthe upper limit of the cold/hot water outlet setting temperatureregistered in advance. When the compensation temperature is higher thanthe upper limit, the upper limit of the cold/hot water outlet settingtemperature is set as the compensation temperature.

Accordingly, it is possible to avoid separation of the supply watertemperature from the target supply water temperature and to preventtrips of the operating heat source machines.

Third Embodiment

A heat source system according to a third embodiment of the presentinvention and a control method thereof will be described below withreference to the accompanying drawings.

In the heat source system according to the second embodiment and thecontrol method thereof, when the compensation temperature is lower thanthe lower limit of the cold/hot water outlet setting temperature or ishigher than the upper limit thereof, the lower limit or the upper limitis set as the compensation temperature.

However, in this treatment, it is difficult to effectively suppress anincrease or a decrease in the supply water temperature. Accordingly, inthis embodiment, in order to cause the operating heat source machines tofurther exercise their capability, the flow rate of the operating heatsource machines is increased. Specifically, the setting flow rate of theoperating heat source machines is changed to the maximum flow ratef_(n_max).

In the heat source system according to this embodiment and the controlmethod thereof, the elements common to the first embodiment will not berepeatedly described and only differences therefrom will be described.

FIGS. 5 to 7 are flowcharts illustrating a supply water temperaturecompensating process according to this embodiment.

First, when an addition or subtraction request is input (“YES” in stepSB1 in FIG. 5), the compensation temperature is calculated (step SB2).In this embodiment, since the setting flow rates of the operating heatsource machines are changed to the maximum flow rate, the calculation ofthe compensation temperature is performed on the basis thereof.Specifically, the compensation temperature T_(set_u) is calculated usingExpression (3).

$\begin{matrix}{T_{{set}\;\_\; u} = \frac{{T_{set}( {{\sum\limits_{i = 1}^{n - 1}f_{i}} + f_{n\;\_\; m\; i\; n}} )} - {f_{n\;\_\; m\; i\; n} \times t_{{ave}\;\_\; r}}}{\sum\limits_{i = 1}^{n - 1}f_{i\_ max}}} & (3)\end{matrix}$

Then, it is determined whether a heat source machine is added (stepSB3). When it is determined that a heat source machine is added (“YES”in step SB3), the cold/hot water outlet setting temperatures of theoperating heat source machines are changed from the target supply watertemperature T_(set) to the compensation temperature T_(set_u) and thecold/hot water setting flow rates thereof are changed to the maximumflow rate (steps SB4 and SB5).

Subsequently, it is determined in step SB6 whether a predeterminedamount of time elapses after the cold/hot water outlet settingtemperatures of the heat source machines are changed to the compensationtemperature or whether the supply water temperature or the cold/hotwater outlet temperatures of the operating heat source machines are inan allowable range set to be close to the compensation temperatureT_(set_u) and whether the flow rate reaches the maximum flow rate. Whenit is determined that the predetermined amount of time elapses or thatthe supply water temperature or the cold/hot water outlet temperaturesof the operating heat source machines are in the allowable range andthat the flow rate reaches the maximum flow rate (“YES” in step SB6), astart instruction is output to the heat source machine to be added andthe flow rate of cold/hot water flowing into the heat source machine isset to the minimum flow rate (step SB7 and step SB8 in FIG. 6).

When the predetermined amount of time elapses from the heat sourcemachine is started or when the cold/hot water outlet temperature of thestarted heat source machine is in the allowable range set to be close tothe target supply water temperature T_(set) (“YES” in step SB9), thecold/hot water outlet setting temperatures of the operating heat sourcemachines are changed from the compensation temperature T_(set_u) to thetarget supply water temperature T_(set) (step SB10), the cold/hot waterflow rates of the operating heat source machines are then returned tothe normal control (step SB11), and then the supply water temperaturecompensating process ends.

On the other hand, when a heat source machine is added and the cold/hotwater outlet setting temperatures of the operating heat source machinesare changed from the target supply water temperature T_(set) to thecompensation temperature T_(set_u) (step SB12 in FIG. 7), the cold/hotwater setting flow rates of the heat source machines continuouslyoperating are changed to the maximum flow rate and the cold/hot watersetting flow rate of the heat source machine to be subtracted is changedto the minimum flow rate (steps SB13). Subsequently, it is determinedwhether a predetermined amount of time elapses after the cold/hot wateroutlet setting temperatures of the heat source machines are changed tothe compensation temperature or whether the supply water temperature orthe cold/hot water outlet temperatures of the operating heat sourcemachines are in an allowable range set to be close to the compensationtemperature T_(set_u) and whether the flow rates of the heat sourcemachines reach the setting flow rates (step SB14).

In this case, similarly to the first embodiment, in step SB12, thecold/hot water outlet setting temperatures of the operating heat sourcemachines except the heat source machine to be subtracted may be changed.In this case, in step SB14, it is determined whether a predeterminedamount of time elapses after the cold/hot water outlet settingtemperatures of the heat source machines are changed to the compensationtemperature or whether the cold/hot water outlet temperatures of theoperating heat source machines except the heat source machine to besubtracted become close to the compensation temperature T_(set_u).

When it is determined that the predetermined amount of time elapses orthat the supply water temperature and the like are in the allowablerange and that the flow rates reach the setting flow rates (“YES” instep SB14), an operation stop instruction is output to the heat sourcemachine to be subtracted and the cold/hot water pump corresponding tothe heat source machine (step SB15).

When it is determined that the predetermined amount of time elapsesafter the heat source machine subtracting instruction is given or thatthe pump corresponding to the heat source machine to be subtracted isstopped (“YES” in step SB16), the cold/hot water outlet settingtemperatures of the operating heat source machines in operation arechanged from the compensation temperature T_(set_u) to the target supplywater temperature T_(set) (step SB17), the cold/hot water flow rates ofthe operating heat source machines are returned to the normal control(step SB18), and then the supply water temperature compensating processends.

As described above, in the heat source system according to thisembodiment and the control method thereof, it is possible to broaden thecontrol width of the supply water temperature by additionally performingthe flow rate control in addition to the temperature control, and it ispossible to cause the operating heat source machines to further exercisetheir capability. Accordingly, it is possible to supplement thecapability shortfall when the heat source machine to be added orsubtracted is additionally started or stopped with the operating heatsource machines as much as possible and it is possible to furthersuppress the variation in the supply water temperature when changing thenumber of heat source machines operating.

The aforementioned flow rate control according to the third embodimentmay be performed, for example, only when the compensation temperatureT_(set_u) calculated in step SA2 in FIG. 2 departs from an upper-lowerrange of the cold/hot water outlet setting temperature which is set inadvance. That is, in this case, it is determined whether thecompensation temperature departs from the upper-lower range of thecold/hot water outlet setting temperature set in advance, and thecompensation temperature is recalculated using Expression (3) when it isdetermined that the compensation temperature departs from the range. Therecalculated compensation temperature is set as the cold/hot wateroutlet setting temperatures of the operating heat source machines, thesetting flow rates of the heat source machines are set to the maximumflow rate, and the setting flow rate of the heat source machine to beadded or subtracted is set to the minimum flow rate.

By employing this configuration, the flow rates can be adjusted only ina situation which cannot be coped with by only changing the temperature,and it is thus possible to skip unnecessary flow rate adjustment.

Fourth Embodiment

A heat source system according to a fourth embodiment of the presentinvention and a control method thereof will be described below withreference to the accompanying drawings.

In the heat source systems according to the first to third embodimentsand the control methods thereof, the variation in the supply watertemperature at the time of changing the number of heat source machinesoperating is suppressed by supplementing the capability shortfall at thetime of starting or stopping the heat source machine to be added orsubtracted by increasing the outputs of the operating heat sourcemachines.

However, for example, at the time of adding a heat source machine, thecapability of the operating heat source machines may reach the upperlimit. In this case, the exercitation of capability of the operatingheat source machines cannot be expected.

Accordingly, in the heat source system according to this embodiment andthe control method thereof, when the capability of the operating heatsource machines reaches the upper limit at the time of adding a heatsource machine, the subsequent determination process is skipped and theheat source machine to be added is rapidly started.

An example of a supply water temperature compensating process accordingto this embodiment will be described below with reference to FIG. 8.

First, when an addition request is input (step SC1), the compensationtemperature T_(set_u) is calculated (step SC2) and the cold/hot wateroutlet setting temperatures are changed from the target supply watertemperature T_(set) to the compensation temperature T_(set_u) (stepSC3), Subsequently, it is determined whether the capability of theoperating heat source machines reaches the upper limit (step SC4). Here,whether the capability of the operating heat source machines reaches theupper limit can be determined, for example, depending on whether thecurrent of a compressor motor reaches a predetermined upper limit,whether a heat source machine load factor reaches a predetermined upperlimit, whether a heat source machine vane opening reaches an upperlimit, and the like. Some of these determinations may be combined.

When it is determined that some operating heat source machines reach theupper limit (“YES” in step SC4), the process of determining whether apredetermined amount of time elapses in step SC5 or the like is skippedand the heat source machine to be added is immediately started (stepSC6). In step SC4, it may be determined whether plural operating heatsource machines (which include all the operating heat source machines)instead of some operating heat source machines reach the upper limit,and the process of determining whether a predetermined amount of timeelapses or the like may be skipped and the heat source machine to beadded may be immediately started when the determination result is “YES”.

When it is determined that the predetermined amount of time elapses fromthe starting of the heat source machine or that the cold/hot wateroutlet temperature of the started heat source machine is in theallowable range set to be close to the target supply water temperatureT_(set) (“YES” in step SC7), the cold/hot water outlet settingtemperatures of the operating heat source machines are changed from thecompensation temperature T_(set_u) to the target supply watertemperature T_(set) (step SC8) and then the supply water temperaturecompensating process ends.

In the heat source system according to this embodiment and the controlmethod thereof, when the capability of the operating heat sourcemachines reaches the upper limit, it is possible to rapidly start theheat source machine to be added without performing subsequentunnecessary determination processes.

This embodiment can be applied by combination with the aforementionedembodiments as well as the first embodiment.

Fifth Embodiment

A heat source system according to a fifth embodiment of the presentinvention and a control method thereof will be described below withreference to the accompanying drawings.

In the heat source systems according to the first to third embodimentsand the control methods thereof, the measured value t_(ave_r) of thereturn water temperature of cold/hot water is used as the cold/hot wateroutlet setting temperature of the heat source machine to be added orsubtracted at the time of calculating the compensation temperature. Thisis because since the capability of the heat source machine is notexercised just after the addition or subtraction and thus the cold/hotwater of the return water temperature flowing from the return header 4is considered to be output from the heat source machine to be added orsubtracted.

However, the measured value of the return water temperature used in thefirst embodiment is a measured value of the return water temperaturebefore the heat source machine to be added or subtracted is started orstopped and is different from the return water temperature after theheat source machine is actually started or stopped.

For example, when the supply water temperature is changed by changingthe number of heat source machines operating, the return watertemperature is also changed accordingly. By this chain reaction, thereis a possibility that the supply water temperature and the return watertemperature slowly rise or fall and may diverge from the original value.

Therefore, in this embodiment, a theoretical value of the return watertemperature is calculated, the theoretical value is considered as thecold/hot water outlet setting temperature of the heat source machine tobe added or subtracted, and the compensation temperature is calculated.

For example, in the schematic configuration of the heat source systemillustrated in FIG. 4, when a request load is Q and the theoreticalvalue of the return water temperature is T_(r_idl), a relationship ofExpression (4) is established between the heat quantity of the cold/hotwater supplied from the supply header 5 to the load side and the heatquantity of the cold/hot water flowing from the return header 4.

$\begin{matrix}{{{Fg} \times \Delta\; t} = {{( {{\sum\limits_{i = 1}^{n - 1}f_{i}} + f_{n\;\_\; m\; i\; n}} ) \times ( {T_{r\;\_\;{idl}} - T_{set}} ) \times c} = Q}} & (4)\end{matrix}$

In Expression (4), Fg represents the flow rate of cold/hot watersupplied to the load side, Δt represents the temperature differencebetween the supply water temperature and the return water temperature,f_(i) represents the flow rate of an operating heat source machine,f_(i_min) represents the flow rate of the heat source machine to beadded or subtracted and is set to the minimum flow rate. T_(set)represents the supply water temperature and c represents the specificheat.

The theoretical value of the return water temperature is given byExpression (5) based on Expression (4).

$\begin{matrix}{T_{r\;\_\;{idl}} = \frac{{Q/c} + {T_{set}( {{\sum\limits_{i = 1}^{n - 1}f_{i}} + f_{n\;\_\; m\; i\; n}} )}}{( {{\sum\limits_{i = 1}^{n - 1}f_{i}} + f_{n\;\_\; m\; i\; n}} )}} & (5)\end{matrix}$

In Expression (2), the compensation temperature T_(set_u) a iscalculated using T_(r_idl) instead of t_(ave_r).

In this way, by using the theoretical value of the return watertemperature as the cold/hot water outlet temperature of the heat sourcemachine to be added or subtracted to calculate the compensationtemperature, it is possible to make the cold/hot water outlettemperature of the heat source machine close to the actual temperature.Accordingly, it is possible to improve the calculation accuracy of thecompensation temperature and to make the supply water temperature closerto the target supply water temperature at the time of changing thenumber of heat source machines operating.

In this embodiment, the cold/hot water outlet temperature of the heatsource machine to be added or subtracted may be calculated using boththe theoretical value T_(r_idl) of the return water temperature and themeasured value t_(ave_r) of the return water temperature. In this case,the compensation temperature is given by Expression (6).

In Expression (6), the cold/hot water outlet temperature of a heatsource machine is obtained by adding values which are obtained byproportionally dividing the theoretical value T_(r_idl) of the returnwater temperature and the measured value t_(ave_r) of the return watertemperature. Specifically, a value obtained by adding a value obtainedby multiplying the theoretical value T_(r_idl) of the return watertemperature by coefficient α (0≤α≤1) and a value obtained by multiplyingthe measured value t_(ave_r) of the return water temperature bycoefficient (1−α) is used as the cold/hot water outlet temperature ofthe heat source machine to be added or subtracted. In Expression (6),the value of a can be arbitrarily set.

$\begin{matrix}{T_{{set}\;\_\; u} = \frac{{T_{set}( {{\sum\limits_{i = 1}^{n - 1}f_{i}} + f_{n\;\_\; m\; i\; n}} )} - {f_{n\;\_\; m\; i\; n} \times ( {{( {1 - \alpha} )t_{{ave}\;\_\; r}} + {\alpha \times T_{r\;\_\;{idl}}}} )}}{\sum\limits_{i = 1}^{n - 1}f_{i}}} & (6)\end{matrix}$

Sixth Embodiment

A heat source system according to a sixth embodiment of the presentinvention and a control method thereof will be described below withreference to the accompanying drawings.

In the heat source system according to the fifth embodiment and thecontrol method thereof, the compensation temperature is calculated inconsideration of the variation of the cold/hot water outlet temperatureof the heat source machine to be added or subtracted, but the variationsin the cold/hot water outlet temperatures of the operating heat sourcemachines are not reflected in the calculation of the compensationtemperature.

That is, when the return water temperature is changed, the cold/hotwater outlet temperatures of the operating heat source machines may beaffected and the cold/hot water outlet temperatures set to thecompensation temperature may not be tracked depending on the operationstates of the operating heat source machines. For example, when thecold/hot water outlet setting temperatures of the operating heat sourcemachines are set to a constant temperature and the cold/hot water inlettemperatures of the operating heat source machines are changed with thechange of the return water temperature, the operating heat sourcemachines are requested to change their capability. In this case, whenthe responses of the operating heat source machines to the changes inthe cold/hot water inlet temperatures are delayed, the cold/hot wateroutlet setting temperatures set to the compensation temperature cannotbe tracked and the cold/hot water outlet temperatures of the operatingheat source machines become different from the cold/hot water outletsetting temperatures. By anticipating this case, in this embodiment, thedifference between the theoretical value of the return water temperatureand the measured value of the return water temperature is included as acorrection value in the expression for calculating the compensationtemperature.

Expression (7) is an operational expression of the compensationtemperature in this embodiment. In Expression (7), the correction valueis expressed as a value obtained by multiplying the difference betweenthe measured value of the return water temperature and the theoreticalvalue of the return water temperature by a predetermined correctioncoefficient β (0≤β≤13),

$\begin{matrix}{T_{{set}\;\_\; u} = {\frac{{T_{set}( {{\sum\limits_{i = 1}^{n - 1}f_{i}} + f_{n\;\_\; m\; i\; n}} )} - {f_{n\;\_\; m\; i\; n} \times ( {{( {1 - \alpha} )t_{{ave}\;\_\; r}} + {\alpha \times T_{r\;\_\;{idl}}}} )}}{\sum\limits_{i = 1}^{n - 1}f_{i}} + {\beta \times ( {t_{{ave}\;\_\; r} - T_{r\;\_\;{idl}}} )}}} & (7)\end{matrix}$

In this way, by including the correction value corresponding to thedifference between the theoretical value of the return water temperatureand the measured value of the return water temperature in theoperational expression of the compensation temperature, it is possibleto set the compensation temperature in consideration of the change inthe cold/hot water outlet temperature due to the cold/hot water inlettemperatures of the operating heat source machines. Accordingly, it ispossible to make the supply water temperature close to the target supplywater temperature even when the measured value of the return watertemperature departs from the theoretical value of the return watertemperature.

Seventh Embodiment

A heat source system according to a seventh embodiment of the presentinvention and a control method thereof will be described below withreference to the accompanying drawings.

In the heat source system according to the fifth or sixth embodiment andthe control method thereof, the compensation temperature is calculatedon the premise that the return water temperature is changed by changingthe number of heat source machines operating.

However, for example, when the flow rate of the heat source machine tobe added is raised at a predetermined change rate, the change in thesupply water temperature due to the heat source machine to be added canbe absorbed by the capability enhancement of the operating heat sourcemachines. Accordingly, it is possible to allow the supply watertemperature to track the target supply water temperature and thus tosuppress the change in the return water temperature.

An example of a supply water temperature compensating process accordingto this embodiment will be described below with reference to FIGS. 9 to11.

First, as illustrated in FIG. 10, in step SD7 of the supply watertemperature compensating process according to this embodiment, thecold/hot water setting flow rate of the heat source machine to be addedis raised to the minimum flow rate at a constant change rate. Here, theconstant change rate is set to be equal to or less than a change rangeat which the supply water temperature can be kept at the target supplywater temperature by exercitation of capability of the operating heatsource machines even when the cold/hot water setting flow rate of theheat source machine to be added is changed at the rate.

Steps SD1 to SD6 and steps SD8 and SD9 correspond to steps SA1 to SA6and steps SA8 and SA9 in FIG. 2 and thus description thereof will not berepeated.

On the other hand, when it is determined in step SD3 (see FIG. 9) that aheat source machine is subtracted, the cold/hot water outlet settingtemperatures of the operating heat source machines except the heatsource machine to be subtracted is changed from the target supply watertemperature T_(set) to the compensation temperature T_(set_u) and thecold/hot water outlet setting temperature of the heat source machine tobe subtracted is changed to a predetermined temperature determined onthe basis of the return water temperature at a constant change rate(steps SD10 and SD11 in FIG. 11). Here, the predetermined temperatureis, for example, a temperature set in advance to be equal to or lowerthan the return water temperature when the heat source system performscooling, and is a temperature set in advance to be equal to or higherthan the return water temperature when the heat source system performsheating.

The constant change rate is set to be equal to or lower than a changerate at which the supply water temperature can track the target supplywater temperature by capability enhancement of the operating heat sourcemachines even when the cold/hot water outlet setting temperature of theheat source machine to be subtracted is changed at the rate.

Subsequently, it is determined whether a predetermined amount of timeelapses after the cold/hot water outlet setting temperatures of theoperating heat source machines except the heat source machine to besubtracted are changed to the compensation temperature or whether thecold/hot water outlet temperatures of the operating heat source machinesexcept the heat source machine to be subtracted are in the allowablerange set to be close to the compensation temperature T_(set_u) (stepSD12). When it is determined that the predetermined amount of timeelapses or that the cold/hot water outlet temperatures of the operatingheat source machines except the heat source machine to be subtracted arein the allowable range, an operation stop instruction is output to theheat source machine to be subtracted and the cold/hot water pumpcorresponding to the heat source machine (step SD13).

Subsequently, it is determined whether a predetermined amount of timeelapses after the heat source machine operation stop instruction isoutput or whether the cold/hot water pump corresponding to the heatsource machine to be subtracted is stopped (step SD14). When it isdetermined that the predetermined amount of time elapses or that thecold/hot water pump is stopped (“YES” in step SD14), the cold/hot wateroutlet setting temperatures of the operating heat source machines arechanged from the compensation temperature T_(set_u) to the target supplywater temperature T_(set) (step SD15) and then the supply watertemperature compensating process ends.

As described above, in the heat source system according to thisembodiment and the control method thereof, when a heat source machine isadded, the change rate of the setting flow rate of the cold/hot water ofthe target heat source machine is set to the trackable range of theoperating heat source machines, and it is thus possible to keep thesupply water temperature close to the target supply water temperature byincreasing the capability of the operating heat source machines.

When a heat source machine is subtracted, the change rate of thecold/hot water outlet setting flow rate of the target heat sourcemachine is set to the trackable range of the operating heat sourcemachines, and it is thus possible to keep the supply water temperatureclose to the target supply water temperature by increasing thecapability of the operating heat source machines. Since the capabilityof the heat source machine to be subtracted is decreased by apredetermined amount before the subtraction, it is possible to suppressthe influence of the subtraction on the system.

Eighth Embodiment

A heat source system according to an eighth embodiment of the presentinvention and a control method thereof will be described below withreference to the accompanying drawings.

In the first embodiment, after the heat source machine to be added orsubtracted is started or stopped, the cold/hot water outlet settingtemperatures of the operating heat source machines are changed from thecompensation temperature to the target supply water temperature. At thistime, when the temperature is gradually changed, the cold/hot wateroutlet temperatures of the operating heat source machines overshoot orundershoot the cold/hot water outlet setting temperatures as illustratedin FIG. 12 and thus there is a possibility that the supply watertemperature is separated from the target supply water temperature afterthe supply water temperature compensating process ends.

Therefore, in this embodiment, an unnecessary overshoot or undershoot isprevented by setting the change rate of the cold/hot water outletsetting temperatures to be slower than normal after the supply watertemperature compensating process ends. The change rate is empiricallyappropriately set to be equal to or less than a change rate at which anovershoot or undershoot does not occur and a specific example of thechange rate is 0,005° C./sec.

In this way, when the cold/hot water outlet setting temperatures arechanged from the compensation temperature to the target supply watertemperature, the change rate at that time is suppressed to be equal toor less than a change rate at which an overshoot or undershoot occursand it is thus possible to avoid occurrence of an overshoot orundershoot, for example, as illustrated in FIG. 13. Accordingly, it ispossible to keep the supply water temperature close to the target supplywater temperature even just after the number of heat source machinesoperating is changed.

Ninth Embodiment

A heat source system according to a ninth embodiment of the presentinvention and a control method thereof will be described below withreference to the accompanying drawings.

In the fourth embodiment, the heat source machine to be added is rapidlystarted when the capability of the operating heat source machinesreaches the upper limit. When plural operating heat source machines arepresent, the capability of some operating heat source machines may reachthe upper limit but the capability of the other operating heat sourcemachines may not reach the upper limit. One reason of this situation isthat the maximum cold/hot water flow rates of the operating heat sourcemachines are different from the rated cold/hot water flow rates. Thatis, when the maximum cold/hot water flow rates are equal to the ratedcold/hot water flow rates and the cold/hot water outlet temperatures areequal to each other, all the heat source machines have the same loadfactor. However, when the maximum cold/hot water flow rates are notequal to the rated cold/hot water flow rates, the load factors of theheat source machines are different from one another even at the samecold/hot water outlet temperature and the heat source machines of whichthe capability reaches the upper limit and the heat source machines ofwhich the capability does not reach the upper limit are present.

In this embodiment, when the operating heat source machines havingreached the capability upper limit and the operating heat sourcemachines not having reached the capability upper limit are mixed, thecapability shortfalls of the operating heat source machines havingreached the capability upper limit are supplemented with the otheroperating heat source machines not having reached the capability upperlimit.

An example of a supply water temperature compensating process accordingto this embodiment will be described below with reference to FIGS. 14 to17.

As illustrated in FIG. 14, in the supply water temperature compensatingprocess according to this embodiment, when a heat source machine isadded, it is determined in step SE5 whether an operating heat sourcemachine of which the capability reaches the upper limit and of which thecold/hot water outlet temperature does not reach the compensationtemperature is present. Steps SE1 to SE4 correspond to steps SA1 to SA4in FIG. 2 and thus description thereof will not be repeated.

When it is determined that an operating heat source machine of which thecapability reaches the upper limit and of which the cold/hot wateroutlet temperature does not reach the compensation temperature ispresent (“YES” in step SE5), it is determined whether another operatingheat source machine of which the capability is less than the upper limitis present (step SE6). When it is determined that such an operating heatsource machine is present (“YES” in step SE6), the compensationtemperature T_(set_ul) of the operating heat source machine isrecalculated using Expressions (8) and (9) (step SE7).

When the determination result of step SE5 or SE6 is “NO”, the processflow goes to step SE9 in FIG. 15 to be described later.

$\begin{matrix}{Q_{lack} = {\sum\limits_{k}{( {t_{{wout}{(k)}} - T_{{set}\;\_\; u}} ) \times f_{k}}}} & (8) \\{T_{{set}\;\_\; u\; 1} = {T_{\;{{set}\;\_\; u}\;} - \frac{Q_{lack}}{\sum\limits_{l}f_{l}}}} & (9)\end{matrix}$

The lack heat quantity Q_(lack) of the operating heat source machine ofwhich the capability has reached the upper limit is calculated usingExpression (8). In Expression (8), k represents an operating heat sourcemachine of which the capability has reached the upper limit and of whichthe cold/hot water outlet temperature has not reached to the settingtemperature, t_(wout) represents the cold/hot water outlet temperatureof the operating heat source machine, and f_(k) represents the flow rateof the heat source machine.

Subsequently, by applying the lack heat quantity Q_(lack) calculatedusing Expression (8) to Expression (9), the compensation temperature ofthe operating heat source machine of which the capability is less thanthe upper limit is recalculated. Specifically, the compensationtemperature is recalculated by dividing the lack heat quantity Q_(lack)by the flow rate of the operating heat source machine of which thecapability is less than the upper limit and subtracting the divisionresult from the compensation temperature. In Expression (9), 1represents the heat source machine of which the capability has notreached the upper limit and of which the cold/hot water outlettemperature has reached the compensation temperature T_(set_u), andT_(set_ul) represents the compensation temperature and is a compensationtemperature for the operating heat source machine.

Subsequently, the compensation temperature T_(set_ul) recalculated usingExpression (9) is set as the cold/hot water outlet setting temperatureof the operating heat source machine (step SE8). Then, it is determinedwhether a predetermined amount of time elapses after the compensationtemperature T_(set_ul) is set as the cold/hot water outlet settingtemperature of the operating heat source machine or whether the supplywater temperature reaches an allowable range set to be close to thecompensation temperature T_(set_u) (step SE9 in FIG. 15). When thecompensation temperature T_(set_ul) for the operating heat sourcemachine is set, it may be determined whether the cold/hot water outlettemperature of the operating heat source machine reaches the allowablerange set to be close to the compensation temperature T_(set_ul). Whenthe compensation temperature T_(set_u) is set for all the operating heatsource machines (“NO” in steps SE5 and SE6), it may be determinedwhether the cold/hot water outlet temperatures of the operating heatsource machines reach the allowable range set to be close to thecompensation temperature T_(set_u).

When this condition is not satisfied (“NO” in step SE9), the processflow is returned to step SE5 and the subsequent processes thereof arerepeatedly performed. Accordingly, in order to distribute the lack heatquantity to the heat source machines with a capability margin, thecold/hot water outlet setting temperature of the operating heat sourcemachine not having reached the capability upper limit is updated everytime.

When the condition of step SE9 is satisfied (“YES” in step SE9), anaddition instruction is output to the heat source machine to be added(step SE10) and then the processes of steps SE11 to SE13 are performed.The processes of steps SE11 to SE13 correspond to steps SA7 to SA9 inFIG. 2 and thus description thereof will not be repeated.

Similarly, when it is determined in step SE3 that a heat source machineis subtracted, the processes of steps SE14 and SE15 in FIG. 16 areperformed and then the process flow goes to step SE16. The processes ofsteps SE14 to SE15 correspond to steps SA10 to SA11 in FIG. 3 and thusdescription thereof will not be repeated. In step SE16, it is determinedwhether an operating heat source machine of which the capability hasreached the upper limit and of which the cold/hot water outlettemperature has not reached the compensation temperature is present.When it is determined that an operating heat source machine of which thecapability has reached the upper limit and of which the cold/hot wateroutlet temperature has not reached the compensation temperature (“YES”in step SE16), it is determined whether an operating heat source machineof which the capability is less than the upper limit and of which thecold/hot water outlet temperature has reached the compensationtemperature is present (step SE17).

When it is determined that such an operating heat source machine ispresent (“YES” in step SE17), the compensation temperature T_(set_ul) ofthe operating heat source machine is calculated using Expressions (8)and (9) (step SE18) and the recalculated compensation temperatureT_(set_ul) is set as the cold/hot water outlet setting temperature ofthe operating heat source machine (step SE19).

When the determination result of step SE16 or SE17 is “NO”, the processflow goes to step SE20.

Subsequently, it is determined whether a predetermined amount of timeelapses after the cold/hot water outlet setting temperature is finallychanged or whether the supply water temperature is in an allowable rangeset to be close to the calculated compensation temperature T_(set_u)calculated in step SE3 (step SE20). Here, as described above, when thecompensation temperature T_(set_ul) is set for the operating heat sourcemachine, it may be determined whether the cold/hot water outlettemperature of the operating heat source machine reaches an allowablerange set to be close to the compensation temperature T_(set_ul). Whenthe compensation temperature T_(set_u) is set for all the operating heatsource machines (“NO” in steps SE16 and SE17), it may be determinedwhether the cold/hot water outlet temperatures of the operating heatsource machines are in the allowable range set to be close to thecompensation temperature T_(set_u).

When this condition is not satisfied (“NO” in step SE20), the processflow is returned to step SE16 and the subsequent processes are repeated.Accordingly, in order to distribute the lack heat quantity to the heatsource machines with a capability margin, the cold/hot water outletsetting temperature of the operating heat source machine not havingreached the capability upper limit is updated every time.

When it is determined that the predetermined amount of time elapsesafter the cold/hot water outlet setting temperature is finally changedor that the supply water temperature is in the allowable range (“YES” instep SE20), a subtraction instruction is output to the heat sourcemachine to be subtracted (step SE21 in FIG. 17) and then the processesof steps SE22 to SE23 are performed. The processes of steps SE22 to SE23correspond to steps SA14 to SA15 in FIG. 3 and thus description thereofwill not be repeated.

As described above, in the heat source system according to thisembodiment and the control method thereof, at the time of adding orsubtracting a heat source machine, when the cold/hot water outletsetting temperatures of the operating heat source machines are changedto the compensation temperature and an operating heat source machinewhich cannot track the compensation temperature due to the capabilityshortfall thereof is present, the capability shortfall can besupplemented with the operating heat source machines not having reachedthe capability upper limit. Accordingly, it is possible to effectivelyuse the capability of the operating heat source machines.

Tenth Embodiment

A heat source system according to a tenth embodiment of the presentinvention and a control method thereof will be described below withreference to the accompanying drawings.

In the first embodiment, for example, at the time of adding a heatsource machine, the cold/hot water outlet temperature of the heat sourcemachine to be added is considered to be the return water temperature(the cold/hot water inlet temperature) and the compensation temperatureis calculated. However, since the heat source machine to be addedgradually exercises the heat source capability after being started, thecold/hot water outlet temperature thereof becomes slowly different fromthe cold/hot water inlet temperature (return water temperature).

Accordingly, since a heat quantity other than anticipated is sent outfrom the added heat source machine, it is difficult to keep the supplywater temperature close to the target supply water temperature. Forexample, when the heat source system cools a heat medium, the cold/hotwater outlet temperature is set to a temperature lower than the cold/hotwater inlet temperature of the heat source machine to be added and theheat medium is supplied. Accordingly, the supply water temperature maybe much lower than the target supply water temperature.

Accordingly, in this embodiment, only at the time of adding a heatsource machine, the compensation temperature of each operating heatsource machine is calculated in consideration of the cold/hot wateroutlet temperature of the heat source machine to be added after the heatsource machine is added.

Specifically, after a heat source machine to be added is added and thecold/hot water pump of the heat source machine is started, thecompensation temperature is calculated using the measured value of thecold/hot water outlet temperature instead of the return watertemperature. The calculation expression of the compensation temperatureis given by Expression (10). The compensation temperature is used as thecold/hot water outlet setting temperatures of the operating heat sourcemachines (the operating heat source machines except the added heatsource machine) after the heat source machine to be added is started.

$\begin{matrix}{T_{{set}\;\_\; u} = \frac{{T_{set}( {{\sum\limits_{i = 1}^{n - 1}f_{i}} + f_{n\;\_\; m\; i\; n}} )} - {f_{n\;\_\; m\; i\; n} \times t_{{wout}{(n)}}}}{\sum\limits_{i = 1}^{n - 1}f_{i}}} & (10)\end{matrix}$

In Expression (10), t_(wout(n)) represents the cold/hot water outlettemperature of the heat source machine to be added.

Instead of the aforementioned method, for example, the return watertemperature and the measured value of the cold/hot water outlettemperature of the heat source machine to be added may be compared andthe compensation temperature may be calculated using the lowertemperature. In this case, the calculation expression of thecompensation temperature is given by Expression (11). Expression (11)represents a case in which the heat source system cools a heat mediumand is to calculate the compensation temperature using the highertemperature when the heat source system heats the heat medium.

$\begin{matrix}{T_{{set}\;\_\; u} = \frac{{T_{set}( {{\sum\limits_{i = 1}^{n - 1}f_{i}} + f_{n\;\_\; m\; i\; n}} )} - {f_{n\;\_\; m\; i\; n} \times {{Min}( {T_{{ave}\;\_\; r},t_{{wout}{(n)}}} )}}}{\sum\limits_{i = 1}^{n - 1}f_{i}}} & (11)\end{matrix}$

In this way, since the compensation temperatures of the operating heatsource machines are calculated in consideration of the change in thecold/hot water outlet temperature of the heat source machine to be addedafter the heat source machine to be added is started, it is possible tocontrol the supply water temperature so as to be close to the targetsupply water temperature even while the heat source machine to be addedgradually exercises its capability.

Eleventh Embodiment

A heat source system according to an eleventh embodiment of the presentinvention and a control method thereof will be described below.

In the first embodiment, for example, at the time of adding a heatsource machine, the compensation temperature is calculated byconsidering the cold/hot water outlet temperature of the heat sourcemachine to be added as the return water temperature (cold/hot waterinlet temperature). However, the cold/hot water in the stopped heatsource machine may not reach the return water temperature because thecold/hot water pump is stopped. For example, in the midsummer, there isa possibility that the temperature of the cold/hot water in the stoppedheat source machine will be much higher than the return watertemperature. In this case, the cold/hot water having a temperature otherthan the anticipated temperature is sent out from the added heat sourcemachine and it is difficult to keep the supply water temperature closeto the target supply water temperature.

Therefore, in this embodiment, the temperature of the cold/hot water inthe heat source machine to be added, for example, the cold/hot wateroutlet temperature or the cold/hot water inlet temperature of the heatsource machine to be added is measured by the temperature sensor and thecompensation temperature using the sensor-measured value instead of thereturn water temperature.

For example, the compensation temperature is calculated by Expression(12).

$\begin{matrix}{T_{{set}\;\_\; u} = \frac{{T_{set}( {{\sum\limits_{i = 1}^{n - 1}f_{i}} + f_{n}} )} - {f_{n} \times t_{n}}}{\sum\limits_{i = 1}^{n - 1}f_{i}}} & (12)\end{matrix}$

In Expression (12), T_(set_u) represents the cold/hot water outletsetting temperature (—compensation temperature) of an operating heatsource machine, T_(set) represents the target supply water temperature,and f_(i) represents the flow rate of cold/hot water flowing in anoperating heat source machine, where f_(i_max) is used as f_(i), forexample, when the setting flow rate of the operating heat source machineis changed to the maximum flow rate as in the third embodiment. f_(n)represents the flow rate of a heat source machine to be added(hereinafter, referred to as “added heat source machine”) and employs,for example, the flow rate set at the time of starting the added heatsource machine. t_(n) represents the temperature of the cold/hot waterof the added heat source machine and is set, for example, to the heatsource machine inlet temperature or the heat source machine outlettemperature measured by the temperature sensor, t_(n) may employ any oneof the air temperature, the air wet-bulb temperature, and the saturatedtemperature of the added heat source machine (which may be the saturatedtemperature determined from the inside pressure) before starting theadded heat source machine.

In this way, according to this embodiment, the heat source machine inlettemperature or the heat source machine outlet temperature of the addedheat source machine is measured by the temperature sensor and thecompensation temperature is calculated using the sensor-measured valueinstead of the return water temperature. Accordingly, even when thetemperature of the cold/hot water in the added heat source machine isseparated from the return water temperature, it is possible to keep thesupply water temperature close to the target temperature.

Twelfth Embodiment

A heat source system according to a twelfth embodiment of the presentinvention and a control method thereof will be described below.

For example, in the eleventh embodiment, the influence to the returnwater temperature is great depending on the temperature of the cold/hotwater in the stopped heat source machine, the capability exercitation ofthe operating heat source machines is not tracked, and it is thusdifficult to keep the supply water temperature close to the targettemperature.

Therefore, in this embodiment, by setting the flow rate of cold/hotwater flowing out of the added heat source machine to be as low aspossible before the added heat source machine is started, the influencewhich the cold/hot water sent out from the added heat source machinegives to the supply water temperature and the return water temperatureis decreased.

An example of a supply water temperature compensating process accordingto this embodiment will be described below with reference to FIGS. 18and 19.

First, when an addition or subtraction request is input (“YES” in stepSF1 in FIG. 18), the compensation temperature is calculated (step SF2).For example, Expression (13) can be used to calculate the compensationtemperature.

$\begin{matrix}{T_{{set}\;\_\; u} = \frac{{T_{set}( {{\sum\limits_{i = 1}^{n - 1}f_{i}} + f_{n}} )} - {f_{n} \times t_{n}}}{\sum\limits_{i = 1}^{n - 1}f_{i}}} & (13)\end{matrix}$

In Expression (13), T_(set_u) represents the cold/hot water outletsetting temperature (—compensation temperature) of an operating heatsource machine, T_(set) represents the target supply water temperature,and f_(i) represents the flow rate of cold/hot water flowing in anoperating heat source machine, where f_(i_max) is used as f_(i), forexample, when the setting flow rate of the operating heat source machineis changed to the maximum flow rate as in the third embodiment, f_(n)represents the flow rate of a heat source machine to be added(hereinafter, referred to as “added heat source machine”) and employs,for example, the flow rate of the pump before starting the added heatsource machine and the minimum flow rate of the added heat sourcemachine after starting the added heat source machine. t_(n) representsthe temperature of the cold/hot water of the added heat source machineand is set, for example, to the heat source machine inlet temperature orthe heat source machine outlet temperature measured by the temperaturesensor. t_(n) may employ any one of the air temperature, the airwet-bulb temperature, and the saturated temperature of the added heatsource machine (which may be the saturated temperature determined fromthe inside pressure) before starting the added heat source machine.

Subsequently, it is determined whether a heat source machine is added(step SF3). When it is determined that a heat source machine is added(“YES” in step SF3), the cold/hot water outlet setting temperatures ofthe operating heat source machines are changed from the target supplywater temperature T_(set) to the compensation temperature T_(set_u)(step SF4).

Subsequently, it is determined whether a predetermined amount of timeelapses after the cold/hot water outlet setting temperatures of the heatsource machines are changed to the compensation temperature or whetherthe supply water temperature or the cold/hot water outlet temperaturesof the started heat source machines are in an allowable range set to beclose to the compensation temperature T_(set_u) (in step SF5). When itis determined that the predetermined amount of time elapses or that thesupply water temperature or the cold/hot water outlet temperatures ofthe started heat source machines are in the allowable range (“YES” instep SF5), a start instruction is output to the cold/hot water pumpcorresponding to the added heat source machine and the frequency of thecold/hot water pump is set to the frequency corresponding to the minimumflow rate of the pump (steps SF6 and SF7).

Subsequently, it is determined whether a predetermined amount of timeelapses after starting the cold/hot water pump or whether the cold/hotwater outlet (inlet) temperature of the added heat source machine is inan allowable range set to be close to the return water temperature (stepSF8 in FIG. 19). When it is determined that the predetermined amount oftime elapses or whether the cold/hot water outlet (inlet) temperature isin the allowable range (“YES” in step SF8), the setting frequency of thecold/hot water pump corresponding to the added heat source machine ischanged to the frequency corresponding to the minimum flow rate of thepump (step SF9).

Subsequently, it is determined whether a predetermined amount of timeelapses after the setting frequency of the cold/hot water pump ischanged or whether the supply water temperature or the cold/hot wateroutlet temperatures of the operating heat source machines are in anallowable range set to be close to the compensation temperatureT_(set_u) and whether the flow rate of the cold/hot water pump reachesthe heat source machine minimum flow rate. When it is determined thatthe predetermined amount of time elapses or that the supply watertemperature or the cold/hot water outlet temperatures of the operatingheat source machines are in the allowable range and that the flow ratereaches the heat source machine minimum flow rate (“YES” in step SF10),a start instruction is output to the added heat source machine (stepSF11).

When it is determined that the predetermined amount of time elapsesafter starting the heat source machine or that the cold/hot water outlettemperature of the started heat source machine is in the allowable rangeset to be close to the target supply water temperature T_(set) (“YES” instep SF12), the cold/hot water outlet setting temperatures of theoperating heat source machines are changed from the compensationtemperature T_(set_u) to the target supply water temperature T_(set)(step SF13) and then the supply water temperature compensating processends.

When it is determined in step SF3 that a heat source machine issubtracted, the process flow goes to step SF15 and the subtractioncontrol according to any one of the aforementioned embodiments isperformed.

As described above, in the heat source system according to thisembodiment and the control method thereof, the cold/hot water flow rateof the heat source machine to be added is set to be as small as possiblebefore starting the heat source machine to be added, and is then raisedto the minimum flow rate of the heat source machine to be added.Specifically, at the time of adding a heat source machine, the cold/hotwater pump corresponding to the added heat source machine is operated atthe frequency (the frequency corresponding to the minimum flow rate ofthe cold/hot water pump) corresponding to the flow rate lower than theminimum flow rate of the heat source machines, the added heat sourcemachine is started on the basis of the relationship of the supply watertemperature and the like, and the setting frequency of the cold/hotwater pump is changed to the frequency corresponding to the minimum flowrate of the added heat source.

In this way, by operating the cold/hot water pumps in a bundle beforestarting the added heat source machine, it is possible to supply thecold/hot water in the added heat source at a low flow rate and it isthus possible to reduce the influence of the cold/hot water of the addedheat source on the supply water temperature in comparison with the otherembodiments. Accordingly, for example, even when the temperature of thecold/hot water in the stopped heat source machine is separated from thereturn water temperature, it is possible to reduce the variation in thesupply water temperature due thereto.

The setting of the flow rate of the added heat source machine is notlimited to two steps as described above, but may be performed in two ormore steps, for example, continuously from the minimum flow rate of thecold/hot water pump to the heat source machine minimum flow rate.

Thirteenth Embodiment

A heat source system according to a thirteenth embodiment of the presentinvention and a control method thereof will be described below.

As illustrated in FIG. 1, in the heat source system 1 in which pluralheat source machines 10 a, 10 b, and 10 c are connected in parallel, theinfluences which the supply water from the heat source machines gives tothe supply water temperature may be different from each other inconstruction of pipes. For example, when a heat source machine disposedin the vicinity of the supply header 5 and a heat source machinedisposed in the vicinity of the bypass pipe 6 are present, the supplywater from the heat source machine disposed in the vicinity of thesupply header 5 gives a greater influence to the supply watertemperature than the supply water from the heat source machine disposedin the vicinity of the bypass pipe 6.

Therefore, in this embodiment, the compensation temperature T_(set_u) iscalculated in consideration of the influences which the supply water ofthe heat source machines gives to the supply water temperature.Specifically, the influences which the supply water of the heat sourcemachines gives to the supply water temperature are converted intoweighting coefficients and are multiplied by the cold/hot water flowrates of the heat source machines.

For example, an expression in which the weighting coefficients areapplied to Expression (3) as an expression for calculating thecompensation temperature in the first embodiment is expressed byExpression (14).

$\begin{matrix}{T_{{set}\;\_\; u} = \frac{{T_{set}( {{\sum\limits_{i = 1}^{n - 1}( {\gamma_{i} + f_{i}} )} + {\gamma \times f_{n\;\_\; m\; i\; n}}} )} - {\gamma_{n} \times f_{n\;\_\; m\; i\; n} \times t_{{ave}\;\_\; r}}}{\sum\limits_{i = 1}^{n - 1}( {\gamma_{i} \times f_{i}} )}} & (14)\end{matrix}$

Here, without being limited to the first embodiment, the weighting maybe considered in the calculation expressions for the compensationtemperature according to the embodiments.

In the heat source system according to this embodiment and the controlmethod thereof, since the compensation temperature is calculated inconsideration of the influence which the supply water of each heatsource machine gives to the supply water temperature, it is possible toimprove the calculation accuracy of the compensation temperature.

While the embodiments of the present invention have been described, thepresent invention is not limited to the aforementioned embodiments, butcan be modified in various forms by partially or overall combining theaforementioned embodiments without departing from the gist of thepresent invention.

REFERENCE SIGNS LIST

-   -   1: heat source system    -   2: external load    -   3 a, 3 b, 3 c: cold/hot water pump    -   4: return head    -   5: supply head    -   6: bypass pipe    -   7: bypass valve    -   10 a, 10 b, 10 c: heat source machine    -   20: upper-level controller

The invention claimed is:
 1. A heat source system that includes aplurality of heat source machines connected in parallel to a load and aplurality of water pumps provided to correspond to the plurality of heatsource machines, respectively, and that controls operations of theplurality of heat source machines such that a supply water temperatureof water which is supplied to the load corresponds to a target supplywater temperature which is determined by a load-side request, the heatsource system comprising: a temperature calculator that, when a requestof increasing the number of the heat source machines operating is input,anticipates a case in which a predetermined flow rate is set for one ormore of the plurality of heat source machines to be added beforestarting the one or more of the plurality of heat source machines to beadded and the water pump corresponding to the one or more of theplurality of heat source machines to be added, and that calculates a newwater outlet temperature of a heat source machine in operation as acompensation temperature such that the supply water temperaturecorresponds to the target supply water temperature, the compensationtemperature being repeatedly calculated with a predetermined samplingcycle on the basis of a flow rate of water flowing in the heat sourcemachine in operation and a return water temperature from the load; and atemperature setter that determines whether the one or more of theplurality of heat source machines is needed to start operating accordingto the request of increasing the number of the heat source machinesoperating, and that changes a water outlet setting temperature of theheat source machine in operation to the compensation temperature whenthe one or more of the plurality of heat source machines is needed tostart operating, wherein one or more of the plurality of heat sourcemachines to be added and a water pump corresponding to the one or moreof the plurality of heat source machines to be added are started and asetting flow rate of one or more of the plurality of heat sourcemachines to be added is set to the predetermined flow rate, when apredetermined amount of time elapses after the water outlet settingtemperature of the heat source machine in operation is changed to thecompensation temperature or when the supply water temperature is in anallowable range set to be close to the compensation temperature.
 2. Theheat source system according to claim 1, wherein the predetermined flowrate of the one or more of the plurality of heat source machines to beadded is set within a range equal to or higher than a minimum flow rateof the water pump provided to correspond to the one or more of theplurality of heat source machines to be added and equal to or lower thana minimum flow rate determined on the basis of a specification of theone or more of the plurality of heat source machines to be added.
 3. Theheat source system according to claim 1, wherein it is determinedwhether an operation state of the heat source machine in operationreaches a capability upper limit after at least the water outlet settingtemperature of the heat source machine in operation is set to thecompensation temperature, and the one or more of the plurality of heatsource machine to be added is immediately started when the operationstate of the heat source machine in operation reaches the capabilityupper limit.
 4. The heat source system according to claim 1, wherein thecompensation temperature is recalculated so as to distribute a heatquantity shortfall of the heat source machines to the other heat sourcemachines in operation of which the capability does not reach thecapability upper limit and the water outlet setting temperature of theother heat source machines in operation of which the capability does notreach the capability upper limit is set to the recalculated compensationtemperature when the operation states of some heat source machines inoperation reach the capability upper limit and the water outlettemperature of the heat source machines in operation does not reach thecompensation temperature after the water outlet setting temperature ofat least the heat source machines in operation is set to thecompensation temperature.
 5. The heat source system according to claim1, wherein the temperature calculator calculates a theoretical value ofthe return water temperature from the load on the basis of arelationship among a heat source load, a heat quantity of water sent outfrom the system to the load, and a heat quantity of water flowing intothe system, and calculates the compensation temperature using thetheoretical value of the return water temperature as the return watertemperature.
 6. The heat source system according to claim 1, furthercomprising a temperature sensor configured to measure the return watertemperature from the load, wherein the temperature calculator calculatesa theoretical value of the return water temperature on the basis of arelationship among a heat source load, a heat quantity of water sent outfrom the system to the load, and a heat quantity of water flowing intothe system, and calculates the compensation temperature using the returnwater temperature, which is calculated using both the measured value ofthe return water temperature measured by the temperature sensor and thetheoretical value of the return water temperature.
 7. The heat sourcesystem according to claim 6, wherein the temperature calculatorcalculates the compensation temperature using a correction valueobtained by multiplying a predetermined coefficient equal to or greaterthan zero and equal to or less than 1 by a value, which is obtained bysubtracting theoretical value of the return water temperature from themeasured value of the return water temperature measured by thetemperature sensor.
 8. The heat source system according to claim 1,wherein the temperature calculator calculates the compensationtemperature using the water outlet temperature of the heat sourcemachines in operation, or the lower temperature of the water outlettemperature and the return water temperature when cooling water, or thehigher temperature of the water outlet temperature and the return watertemperature when heating water as the return water temperature after theone or more of the plurality of heat source machines to be added isstarted.
 9. A heat source system that includes a plurality of heatsource machines connected in parallel to a load and a plurality of waterpumps provided to correspond to the plurality of heat source machines,respectively, and that controls operations of the plurality of heatsource machines such that a supply water temperature of water which issupplied to the load corresponds to a target supply water temperaturewhich is determined by a load-side request, the heat source systemcomprising: a temperature calculator that, when a request of decreasingthe number of the heat source machines operating is input, anticipates acase in which a predetermined flow rate is set for one or more of theplurality of heat source machines to be subtracted before stopping theone or more of the plurality of heat source machines to be subtractedand the water pump corresponding to the one or more of the plurality ofheat source machines to be subtracted, and that calculates a new wateroutlet temperature of a heat source machine in operation as acompensation temperature such that the supply water temperaturecorresponds to the target supply water temperature, the compensationtemperature being repeatedly calculated with a predetermined samplingcycle on the basis of a flow rate of water flowing in the heat sourcemachine in operation and a return water temperature from the load; and atemperature setter that determines whether the one or more of theplurality of heat source machines is needed to stop operating accordingto the request of decreasing the number of the heat source machinesoperating, and that changes a water outlet setting temperature of theheat source machine in operation to the compensation temperature whenthe one or more of the plurality of heat source machines is needed tostop operating, wherein the one or more of the plurality of heat sourcemachines to be subtracted is stopped and the water pump corresponding tothe one or more of the plurality of heat source machines to besubtracted is stopped, when a predetermined amount of time elapses afterthe water outlet setting temperature of the heat source machine inoperation is changed to the compensation temperature or when the supplywater temperature or the water outlet temperature of the heat sourcemachine in operation is in an allowable range set to be close to thecompensation temperature.
 10. The heat source system according to claim9, wherein the predetermined flow rate of the one or more of theplurality of heat source machines to be subtracted is set to a minimumflow rate determined on the basis of a specification of the one or moreof the plurality of heat source machines.
 11. The heat source systemaccording to claim 9, wherein the compensation temperature isrecalculated so as to distribute a heat quantity shortfall of the heatsource machines to the other heat source machines in operation of whichthe capability does not reach the capability upper limit and the wateroutlet setting temperature of the other heat source machines inoperation of which the capability does not reach the capability upperlimit is set to the recalculated compensation temperature when theoperation states of some heat source machines in operation reach thecapability upper limit and the water outlet temperature of the heatsource machines in operation does not reach the compensation temperatureafter the water outlet setting temperature of at least the heat sourcemachines in operation is set to the compensation temperature.
 12. Theheat source system according to claim 9, wherein the temperaturecalculator calculates a theoretical value of the return watertemperature from the load on the basis of a relationship among a heatsource load, a heat quantity of water sent out from the system to theload, and a heat quantity of water flowing into the system, andcalculates the compensation temperature using the theoretical value ofthe return water temperature as the return water temperature.
 13. Theheat source system according to claim 9, further comprising atemperature sensor configured to measure the return water temperaturefrom the load, wherein the temperature calculator calculates atheoretical value of the return water temperature on the basis of arelationship among a heat source load, a heat quantity of water sent outfrom the system to the load, and a heat quantity of water flowing intothe system, and calculates the compensation temperature using the returnwater temperature, which is calculated using both the measured value ofthe return water temperature measured by the temperature sensor and thetheoretical value of the return water temperature.
 14. The heat sourcesystem according to claim 13, wherein the temperature calculatorcalculates the compensation temperature using a correction valueobtained by multiplying a predetermined coefficient equal to or greaterthan zero and equal to or less than 1 by a value, which is obtained bysubtracting theoretical value of the return water temperature from themeasured value of the return water temperature measured by thetemperature sensor.
 15. The heat source system according to claim 9,wherein the temperature calculator calculates the compensationtemperature using the water outlet temperature of the heat sourcemachines in operation, or the lower temperature of the water outlettemperature and the return water temperature when cooling water, or thehigher temperature of the water outlet temperature and the return watertemperature when heating water as the return water temperature after theone or more of the plurality of heat source machines to be subtracted isstopped.
 16. A heat source system that includes a plurality of heatsource machines connected in parallel to a load and a plurality of waterpumps provided to correspond to the plurality of heat source machines,respectively, and that controls operations of the plurality of heatsource machines such that a supply water temperature of water which issupplied to the load corresponds to a target supply water temperaturewhich is determined by a load-side request, the heat source systemcomprising: a temperature calculator that, when a request of decreasingthe number of the heat source machines operating is input, anticipates acase in which a predetermined flow rate is set for one or more of theplurality of heat source machines to be subtracted before stopping theone or more of the plurality of heat source machines to be subtractedand the water pump corresponding to the one or more of the plurality ofheat source machines to be subtracted, and that calculates a new wateroutlet temperature of a heat source machine in operation as acompensation temperature such that the supply water temperaturecorresponds to the target supply water temperature, the compensationtemperature being repeatedly calculated with a predetermined samplingcycle on the basis of a flow rate of water flowing in the heat sourcemachine in operation and a return water temperature from the load; and atemperature setter that determines whether the one or more of theplurality of heat source machines is needed to stop operating accordingto the request of decreasing the number of the heat source machinesoperating, and that changes a water outlet setting temperature of theheat source machine in operation other than the one or more of theplurality of heat source machines to be subtracted to the compensationtemperature when the one or more of the plurality of heat sourcemachines is needed to stop operating, and wherein the one or more of theplurality of heat source machines to be subtracted is stopped and thewater pump corresponding to the one or more of the plurality of heatsource machines to be subtracted is stopped, when a predetermined amountof time elapses after the water outlet setting temperature of the heatsource machine in operation is changed to the compensation temperatureor when the water outlet temperature of the heat source machine inoperation other than the one or more of the plurality of heat sourcemachines to be subtracted is in an allowable range set to be close tothe compensation temperature.
 17. A heat source method, in which aplurality of heat source machines connected in parallel to a load and aplurality of water pumps is provided to correspond to the plurality ofheat source machines, for controlling operations of the plurality ofheat source machines such that a supply water temperature of water whichis supplied to the load corresponds to a target supply water temperaturewhich is determined by a load-side request, the heat source methodcomprising: calculating a temperature when a request of increasing thenumber of the heat source machines operating is input; determining acase in which a predetermined flow rate is set for one or more of theplurality of heat source machines to be added before starting the one ormore of the plurality of heat source machines to be added and the waterpump corresponding to the one or more of the plurality of heat sourcemachines to be added; calculating a new water outlet temperature of aheat source machine in operation as a compensation temperature such thatthe supply water temperature corresponds to the target supply watertemperature, the compensation temperature being repeatedly calculatedwith a predetermined sampling cycle on the basis of a flow rate of waterflowing in the heat source machine in operation and a return watertemperature from the load; and determining whether the one or more ofthe plurality of heat source machines is needed to start operatingaccording to the request of increasing the number of the heat sourcemachines operating, and changing, a water outlet setting temperature ofthe heat source machine in operation to the compensation temperaturewhen the one or more of the plurality of heat source machines is neededto start operating, wherein one or more of the plurality of heat sourcemachines to be added and a water pump corresponding to the one or moreof the plurality of heat source machines to be added are started and asetting flow rate of one or more of the plurality of heat sourcemachines to be added is set to the predetermined flow rate, when apredetermined amount of time elapses after the water outlet settingtemperature of the heat source machine in operation is changed to thecompensation temperature or when the supply water temperature is in anallowable range set to be close to the compensation temperature.
 18. Aheat source method, in which a plurality of heat source machinesconnected in parallel to a load and a plurality of water pumps isprovided to correspond, to the plurality of heat source machines, forcontrolling operations of the plurality of heat source machines suchthat a supply water temperature of water which is supplied to the loadcorresponds to a target supply water temperature which is determined bya load-side request, the heat source method comprising: calculating atemperature when a request of decreasing the number of the heat sourcemachines operating is input; determining a case in which a predeterminedflow rate is set for one or more of the plurality of heat sourcemachines to be subtracted before stopping the one or more of theplurality of heat source machines to be subtracted and the water pumpcorresponding to the one or more of the plurality of heat sourcemachines to be subtracted; calculating a new water outlet temperature ofa heat source machine in operation as a compensation temperature suchthat the supply water temperature corresponds to the target supply watertemperature, the compensation temperature being repeatedly calculatedwith a predetermined sampling cycle on the basis of a flow rate of waterflowing in the heat source machine in operation and a return watertemperature from the load; and determining whether the one or more ofthe plurality of heat source machines is needed to stop operatingaccording to the request of decreasing the number of the heat sourcemachines operating, and changing a water outlet setting temperature ofthe heat source machine in operation to the compensation temperaturewhen the one or more of the plurality of heat source machines is neededto stop operating, wherein the one or more of the plurality of heatsource machines to be subtracted is stopped and the water pumpcorresponding to the one or more of the plurality of heat sourcemachines to be subtracted is stopped, when a predetermined amount oftime elapses after the water outlet setting temperature of the heatsource machine in operation is changed to the compensation temperatureor when the supply water temperature or the water outlet temperature ofthe heat source machine in operation is in an allowable range set to beclose to the compensation temperature.
 19. A heat source method, inwhich a plurality of heat source machines connected in parallel to aload and a plurality of water pumps is provided to correspond to theplurality of heat source machines, for controlling operations of theplurality of heat source machines such that a supply water temperatureof water which is supplied to the load corresponds to a target supplywater temperature which is determined by a load-side request, the heatsource method comprising: calculating a temperature when a request ofdecreasing the number of the heat source machines operating is input;determining a case in which a predetermined flow rate is set for one ormore of the plurality of heat source machines to be subtracted beforestopping the one or more of the plurality of heat source machines to besubtracted and the water pump corresponding to the one or more of theplurality of heat source machines to be subtracted; calculating a newwater outlet temperature of a heat source machine in operation as acompensation temperature such that the supply water temperaturecorresponds to the target supply water temperature, the compensationtemperature being repeatedly calculated with a predetermined samplingcycle on the basis of a flow rate of water flowing in the heat sourcemachine in operation and a return water temperature from the load; anddetermining whether the one or more of the plurality of heat sourcemachines is needed to stop operating according to the request ofdecreasing the number of the heat source machines operating, andchanging a water outlet setting temperature of the heat source machinein operation other than the one or more of the plurality of heat sourcemachines to be subtracted to the compensation temperature when the oneor more of the plurality of heat source machines is needed to stopoperating, and wherein the one or more of the plurality of heat sourcemachines to be subtracted is stopped and the water pump corresponding tothe one or more of the plurality of heat source machines to besubtracted is stopped, when a predetermined amount of time elapses afterthe water outlet setting temperature of the heat source machine inoperation is changed to the compensation temperature or when the wateroutlet temperature of the heat source machine in operation other thanthe one or more of the plurality of heat source machines to besubtracted is in an allowable range set to be close to the compensationtemperature.